The hormonal regulation of hepatic carbohydrate metabolism is being examined using isolated hepatocytes from rats. Emphasis is placed on cyclic AMP independent pathways for activation of glycogen phosphorylase. The role of extracellular calcium in the glycogen action of epinephrine or other alpha catecholamines and glucagon was found to be minor. The presence of extracellular calcium or intracellular calcium in readly depleted pools is required for the activation of phosphorylase by vasopressin or the divalent cation ionophore A-23187. In hepatocytes from hypothyroid rats there is an enhanced effect of beta catecholamines with little effect on alpha adrenergic stimulation of glycogenolysis via cyclic AMP independent pathways. Even in calcium-depleted hepatocytes from hypothyroid rats there is an alpha-like activation of phosphorylase independent of measurable cyclic AMP. The other emphasis of this project is on the role of phosphatidylinositol hydrolysis in calcium gating. It is thought that the alpha adrenergic action via the cyclic AMP independent pathways may involve a release of intracellular calcium and uptake of extracellular calcium. We have been able to demonstrated a Ca ion-independent increase in phosphatidylinositol turnover due to alpha adrenergic amines and vasopressin which was not mimicked by glucagon or A-23187. Studies are in progress to elucidate the site and function of phosphatidylinositol hydrolysis in the action of alpha catecholamines, and vasopressin, and insulin.